Abstract
Very recently novel implementation of type-II seesaw mechanism for neutrino mass has been proposed in SU(5) grand unified theory with a number of desirable new physical phenomena beyond the standard model. Introducing heavy right-handed neutrinos and extra fermion singlets, in this work we show how the type-I seesaw cancellation mechanism works in this SU(5) framework. Besides predicting verifiable LFV decays, we further show that the model predicts dominant double beta decay with normal hierarchy or inverted hierarchy of active light neutrino masses in concordance with cosmological bound. In addition a novel right-handed neutrino mass generation mechanism, independent of type-II seesaw predicted mass hierarchy, is suggested in this work.
Highlights
Renormalisable standard model (SM) predicts neutrinos to be massless whereas oscillation experiments prove them to be massive [1,2,3,4,5]
On the basis of SU(5) symmetry alone there may not be any reason for the rigorous validity of eq(35), in what follows we study the implications of this assumed value of MD to examine maximum possible impact on lepton flavor violating (LFV) and lepton number violating (LNV) decays discussed in Sec.6 and Sec
In order to remove these theoretical shortcomings in the context of SU(5), we have extended this model by the addition of three RHνs, three extra Majorana fermion singlets singlet fermions (Si)(i = 1, 2, 3) and a scalar singlet χS(1, 0, 1) that generates N − S mixing mass term through its vacuum expectation value
Summary
Renormalisable standard model (SM) predicts neutrinos to be massless whereas oscillation experiments prove them to be massive [1,2,3,4,5]. This realization is consistent with cosmological bound of eq(1) Such possibilities were realized earlier in SO(10) with TeV scale WR or Z bosons as noted above, in SU(5) without the presence of left-right symmetry and associated gauge bosons, we have shown here for the first time that the dominant double beta decay is mediated by a sterile neutrino (Majorana fermion singlet) of O(1) GeV mass of first generartion. [130], inclusion of the scalar κ(3, 0, 8) ⊂ 75H with mass Mκ = 109.23GeV in the extended non-SUSY SU(5) achieves precision gauge coupling unification It has been shown in [129] that type-II seesaw ansatz for neutrino mass is realized by inserting the entire Higgs multiplet 15H ⊂ SU (5) containing the LH Higgs triplet ∆L(3, −1, 1) at the same mass scale M15H = 1012GeV. Implementation of type-II seesaw dominance due to type-I seesaw cancellation resulting in dominant LFV and LNV decays as dicussed below is new especially in the context of non-SUSY SU(5)
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